Why not a darker grey?

Plus, the ceiling in the porch traditionally could be painted a light blue.

Victorian porch floors were almost always painted a medium gray that is usually called "battleship" gray. I don't think I have ever seen a different color.

You, of course, can paint your floor any color you choose. But the period-accurate color would probably be medium gray.

Without seeing your house, I'd suggest trying a deep cranberry color. It is just paint on something that's already painted. :)

Just an FYI: my porch was grey and I over-painted w/ Colonial Blue and it made it look much better to me. A few years ago I was able to have the old/bad porch floor ripped out and I had it replaced with new natural fir. The finish I applied was marked "natural" so I expected it to be clear, but it contained stain with a barely reddish-golden-brown tint to it. What's interesting to me is the difference in the color of the room that looks out onto the porch!!! the blue porch floor reflected a cool light color into the room... the new stained wood porch floor reflects a very warm yellow-red color into the room -- like it glows. It makes the room look so different! You might want to think about the color you'd like reflected into the rooms that overlook the porch. :)